Blizzard Beach is one of Disney's two waterparks.  For most people, I think the waterparks are kind of an afterthought compared to the four main parks, and probably deservedly so.  This is a great waterpark, and the slides were a lot of fun, but it wasn't significantly better than most any other water park.  Of course, everything's Disney-fied, and it's definitely a well-done water park.  We spent about a half day there, and we rode every ride (I think).  If you have the time and want a break from the main parks, it is worth it.  With the tickets that we had, the waterpark didn't cost us any extra.